Summary of Work: Diet may play a role in immune function, particularly with respect to autoimmunity. Dietary interventions (e.g., antioxidant supplementation, manipulation of the fat content) can prolong survival in murine models of systemic lupus erythematosus (SLE). The role of these dietary factors in the etiology of SLE in humans has not been examined. The objective of this study is to examine the influence of diet on the risk of SLE. We are using data from the Nurses- Health Study, a cohort of 121,000 women ages 30-55 followed with biennial questionnaire assessment since 1976. Food frequency and nutritional supplement data were collected from 93,184 members of this cohort in 1980. Data on SLE occurrence were collected in 1982, 1984, 1986, and 1992. Two rheumatologists independently reviewed medical records and verified 57 SLE cases diagnosed after the 1980 diet assessment. We calculated incidence rates and rate ratios from 1980-1990 for each quintile of energy-adjusted nutrient intake. SLE incidence decreased somewhat with higher intakes of Vitamin C and E: rate ratios (RR) and 95% confidence intervals comparing the highest to the lowest quintiles of intake (including supplements) were 0.52 (0.21- 1.3) for vitamin C and 0.52 (0.22-1.2) for vitamin E, and tests for trend were p=0.20 and 0.36, respectively. This was not seen when we excluded supplement users: for vitamin C, RR=1.1 (0.42-2.8) and for vitamin E, RR=0.89 (0.36-2.2). There was little evidence for an association with vitamin A or total fat intake. Future analyses will use updated nutrient data from the 1984 and 1986 assessments and will include additional cases diagnosed from 1990 to 1996.